Strange flavors in white pepper

As I noted in my previous post, in this week's New York Times column I wrote about the recent discovery of the molecule that contributes the distinctive peppery aroma to black and white pepper--and to Syrah wines. Along the way, I also described some of the strange and not very pleasant aromas that white pepper can have, which range from barnyardy to plastic to medicinal. It was the plastic-medicinal quality that gave away the problem with some really bad pommes purées at a Midtown restaurant: they had been white-peppered to death.

In the printed version of the column, the third-to-last paragraph suggests that all white pepper carries these unpleasant notes. This is not true.

Fresh peppercorns are small fruits. They consist of a large, light-colored seed surrounded by a thin fleshy layer, which turns from green to red as the peppercorn ripens. When the still-green peppercorn is harvested and dried, the outer layer turns black: hence black pepper. To make white pepper, the producers pick the peppercorns when they're ripe and the outer layer soft, put them into bags or barrels, and submerge them in water to ferment for as much as two weeks. The outer fleshy layer rots away, and the light seeds are then dried.

White pepper is valued by chefs and in food manufacturing for the fact that it provides pepper flavor without any unsightly little black specks. But the high incidence of flavor defects has been enough of a problem in the food industry that chemists in Germany set out to investigate it.

It turns out that the off-flavors develop during the fermentation. Pepper is grown and white pepper produced in the tropics, and thanks to the heat and the stagnant fermentation water, microbes flourish that break down peppercorn flesh to variations on the molecule indole and other compounds that smell rotten, fecal, cheesy, and chemical. The chemists showed that if the peppercorns are kept in constantly flowing water for just a few days, the fleshy layer can be removed with little or no development of off-flavors. This discovery should result in improved fermentation hygiene and more consistently clean-smelling white pepper.

In the meantime it's worth knowing that white pepper has this potential for carrying off-flavors. Taste it before cooking with it. Occasionally the funkiness can actually work. In hot-and-sour soup, for example, some recipes for which do specify white pepper, I find that it makes a positive contribution to all the commotion.

It's also interesting that according to the Australian study of the pepper aromatic, rotundone, white pepper contains more than twice as much rotundone as black pepper. This means that the same dose of white pepper will produce much more peppery aroma than black pepper. (At high doses, rotundone goes from smelling peppery to smelling harsh and burned.) Why should this be the case? Peppercorns for white pepper are harvested when the fruit is ripe, and it may be that rotundone levels go up as the fruits ripen.